1. Field of the invention
This invention relates to onboard monitoring of emission control components in an automobile vehicle having an internal combustion engine.
2. Prior Art
It is known to use catalysts in the exhaust stream of an automobile in order to reduce undesired components of the exhaust. It is also known to monitor whether the catalyst is operating properly. One way of doing this is to have exhaust gas oxygen sensors both upstream and downstream of the catalyst. The output signals from these two sensors are compared to make a determination about the operation of the catalyst located between the two exhaust gas oxygen (EGO) sensors. However, such a method assumes proper operation of the EGO sensors.
It is known that the EGO sensor can be removed from the vehicle and tested in a laboratory to determine proper operation. However, this is not a practical method, and it would be desirable to have a method whereby the EGO sensor can be tested while still installed on the vehicle. These are some of the problems this invention overcomes.